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Men suffering mid-life crises sometimes act like teenagers, zooming around in sports cars, staying out late, and -- coming down with "mono"?

Upwards of 10 percent of adults may be susceptible to the enervating "kissing sickness," and diagnosing it can be tricky, says Paul Auwaerter, M.D., Johns Hopkins infectious disease specialist.

While in teenagers infectious mononucleosis, or "mono," typically begins with fatigue, fever, sore throat and swollen lymph nodes, symptoms in adults vary widely. "When people get in their 30s and older, it no longer resembles typical mono," says Auwaerter. "They usually get the fever but not the other symptoms typical in teenagers. It can masquerade as other syndromes."

That's exactly what happened with a 42-year-old man who had a persistent fever and a series of other ailments, including pneumonia. The man made several trips to the clinic, leaving doctors puzzled when tests for hepatitis and other diseases were negative. When Auwaerter was called in on the case, he inspected the patient's blood and found twisted, deformed white cells -- a telltale sign of mono. A sensitive antibody test confirmed the diagnosis.

Eighty years before Auwaerter solved that minor mystery, when mono was not yet known, two Hopkins pathologists confronted a similar puzzle. After examining the blood of six young patients with the typical symptoms of mono, the physicians saw the misshapen cells. They feared the worst: leukemia. But in a matter of weeks, the six patients recovered without treatment, leading the doctors to conclude an acute, unknown infection was the culprit. They wrote a thorough description of the case -- possibly the first -- and published it in a 1920 issue of the now-defunct Johns Hopkins Hospital Bulletin.

Today, scientists know infectious mononucleosis is caused by the Epstein-Barr virus (which also has been linked to some cancers) and is often spread via saliva. Like chicken pox virus, Epstein-Barr exposure inoculates against further infection, making it uncommon in adults.

A description of Auwaerter's case can be found in the Feb. 3 Journal of the American Medical Association.

New research from Johns Hopkins shows that hearing is a biochemical process, not simply a mechanical vibration of the organs of the inner ear. By explaining how tiny hair cells inside the ear respond to different pitches at the molecular level, the work also provides a target for further studies into causes of and cures for hearing loss.

Led by Paul Fuchs, Ph.D., professor of otolaryngology-head and neck surgery, the Hopkins team identified and cloned genes for certain proteins in hair cells, which lie along the spiral-shaped cochlea. One of the proteins, dubbed the beta chain, is spread along the cochlea in a gradient that suggests it is crucial for hearing low frequencies.

The cochlear proteins build small channels that allow potassium ions to flow into and out of the hair cells. Previous work showed that the speed with which these potassium channels open and close is related to the frequency of sound: Lower sound means slower potassium. Fuchs set out to discover why, at the molecular level, this was so.

His team found that one of the channel-building proteins, the alpha chain, occurs in several forms and is distributed evenly across the cochlea. But whenever a beta chain was added to an alpha-chain channel, potassium currents slowed down, "as though the beta chain ought to occur in low frequency hair cells," says Fuchs. Further work showed that the beta chain does indeed bunch up at the wide, floppy end of the organ, the region where low frequency sounds are perceived.

Knowing the structure and genetics of the ion channels is of particular interest because the channels regulate calcium flow into the hair cells. Too much calcium kills the cells, which are essential for hearing.

"We'd like to look at gene products like these potassium channels in the context of aging, to see if they might be involved in age-related hearing loss," said Fuchs.

Along with co-authors Krishnan Ramanathan, Timothy H. Michael, Guo-Jian Jiang and Hakim Hiel, Fuchs published the study in the January 8, 1999, issue of Science.

PREVENT ILLNESS WHEN TRAVELING THIS SPRING

You wouldn't leave home without your suitcase, tickets and itinerary, yet many people travel without another essential -- a medical check-up.

Experts at Johns Hopkins Travel Medicine and Immunization Service, one of the oldest travel clinics in the country, say a pre-departure consultation is the key to decreasing the risk of illness and injury while traveling abroad.

"We practice 100 percent preventative medicine," says Judy Baker, M.P.H., the clinic's assistant director. Bradley Sack, M.D., Baker and the rest of the clinic staff have all lived and worked abroad extensively, offering their hands-on expertise to travelers for 13 years.

The Hopkins clinic offers up-to-date information tailored to each traveler's health past and travel future. Individual, family and group consultations, vaccinations, prescriptions, and reference materials are available, as are post-travel diagnosis and treatment. Baker says of the clinic's 4,000 annual visits, only 5 percent are for post-travel illness.

The clinic continues to prepare all types of travelers, including adventure seekers, disaster relief workers, and a growing number of couples headed abroad to adopt.

The clinic's experts offer these healthy travel tips:

* Get immunized -- Diseases that are virtually unknown in northern climes are more common in popular tropical destinations. Vaccines for hepatitis A and B, yellow fever, typhoid and other diseases are available. In addition, medicine to prevent malaria can be prescribed.

* Prevent diarrhea -- Bacteria, viruses and parasites can all cause this unwelcome annoyance, which can leave travelers dehydrated and exhausted. Most cases are transmitted through tainted food or water, so drink only bottled or boiled water. Also beware of unpasteurized dairy and uncooked or unpeeled foods. Over-the-counter preparations can counteract symptoms but do not cure diarrhea. Oral rehydration solution and a short course of antibiotics are prescribed for severe cases.

* Combat jet lag -- Melatonin, a sleep-regulating hormone sold over-the-counter, can readjust your biological clock when taken at the right times. On the day of departure, take one three to five mg tablet one hour before your destination's bedtime. Then take one tablet for three to five nights, before bedtime, upon arrival.

* Plan -- Keep medications in your carry-on luggage, take along a medicine kit, and know where to find help in case of emergencies. Practice safe sex and pack sunscreen.

To schedule an appointment at the clinic, call 410-955-8931.

More information on travel medicine is available on the Internet at www.hopkins-id.edu. Click on "Travel Medicine" at the top of the page.

To arrange an interview with the clinic staff or its traveling patients, call Brian Vastag at (410) 955-8665 or e-mail bvastag@jhmi.edu.

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